Method and apparatus for activating an electric machine, and electric machine

ABSTRACT

A method of activating an electric machine having a stator, and a rotor which rotates about an axis with respect to the stator; the stator having a plurality of stator segments arranged about the axis; the rotor having modules made of magnetizable material and arranged about the axis; and the method including the steps of connecting the rotor to the stator by means of a bearing; and magnetizing the modules of magnetizable material when the rotor is connected to the stator.

PRIORITY CLAIM

This application is a continuation of, claims the benefit of andpriority to U.S. patent application Ser. No. 12/851,782, filed on Aug.6, 2010, which claims the benefit of and priority to Italian PatentApplication No. MI2009A 001443, filed on Aug. 7, 2009, the entirecontents of which are each incorporated by reference herein.

BACKGROUND

Known electric machines comprises a stator, and a rotor which rotatesabout an axis with respect to the stator.

In these known electric machines, the stator comprises an outercylinder, and stator segments arranged about the axis. The rotorcomprises an inner cylinder, and rotor segments arranged about the axis;and each rotor segment comprises modules made of magnetizable materialand arranged, parallel to the axis, inside the rotor segment.

To activate such known electric machines, the modules of magnetizablematerial must be magnetized (i.e., a material or object that produces amagnetic field). More specifically, each module of magnetizable materialis made of material that can be magnetized to produce a magnetic field.This is done by adopting an electric machine activating method, whichcomprises a module magnetizing step, after and by virtue of which eachmodule produces a magnetic field and is known as a magnetized module.

The magnetizing step is performed by a magnetizing device, whichmagnetizes the modules of magnetizable material with magnetizing flux ofa given strength.

The strength of the magnetic field produced by each module changes, inparticular gets weaker, over the working life of the module, so that,after a certain time period, normally ranging between ten and twentyyears, each module is no longer capable of producing a magnetic fieldcapable of effectively interacting with the magnetic field produced bythe stator, with the result that the machine is no longer active, andmust therefore be reactivated by remagnetizing the modules. Thisinvolves further magnetization of the previously magnetized modules,which, once remagnetized, define magnetized modules in all respects.

Such known electric machines are typically activated by: magnetizingeach module; fitting each magnetized module to the inner cylinder of therotor; fitting the stator segments to the stator; and connecting therotor, with the magnetized modules, to the stator with one or morebearings.

However, this known method poses the technical problem of having tohandle each magnetized module, which is a dangerous job on account ofthe module generating strong forces which interact with other modules orferromagnetic parts. That is, when fitting each magnetized module to therotor, the magnetized modules already fitted to the rotor interact withthe one being assembled. For this reason, the magnetized modules must beassembled using special tools and in premises designed for the job. Morespecifically, in the case of an electric machine that has never beenoperated, the magnetizing step is performed at the factory; whereas, ifthe electric machine forms part of a system and needs reactivating, itmust be dismantled from the system and sent to the factory, and eachmodule or group of modules must be removed, and each group of modulesremagnetized. This is obviously a long, painstaking procedure involvingnumerous man-hours and considerable cost, and which also calls fortransporting an electric machine with the rotor magnetized.

SUMMARY

The present disclosure relates to a method and apparatus for activatingan electric machine, and to an electric machine.

It is an object of the present disclosure to provide a method ofactivating an electric machine, configured to eliminate certain of theabove-described drawbacks of known electric machines.

According to one embodiment of the present disclosure, there is provideda method of activating an electric machine; the electric machinecomprising a stator, and a rotor which rotates about a first axis withrespect to the stator; the stator comprising a plurality of statorsegments arranged about the first axis; the rotor comprising modulesmade of magnetizable material and arranged about the first axis; and themethod comprising the steps of connecting the rotor to the stator by abearing; and magnetizing said modules of magnetizable material when therotor is connected to the stator.

In the method according to the present disclosure, the electric machineis activated by magnetizing the modules after the rotor is fitted to thestator, thus eliminating problems posed by handling magnetized modules.Moreover, according to the present disclosure, the magnetizing step isperformed after almost all the stator segments have been fitted to theouter cylinder (i.e., it need not necessarily be carried out at thefactory, and may be performed after the electric machine is installed,for example, in the nacelle of a wind power turbine, or in a cabletransportation system). The present disclosure also avoids transportingthe electric machine with the rotor magnetized. In fact, the electricmachine can be fitted with the non-magnetized rotor and part of thestator comprising almost all the stator segments, and be activated, bymagnetizing the rotor, after it is installed, thus eliminating anyinteracting Forces when assembling or transporting the electric machine.

The present disclosure also allows the electric machine to bereactivated by remagnetizing the rotor directly on the system in whichthe electric machine is installed, thus saving time with respect toknown electric machines.

Another object of the present disclosure is to provide an apparatus foractivating an electric machine, configured to eliminate certain of theabove-described drawbacks of known electric machines.

According to one embodiment of the present disclosure, there is providedan apparatus for activating an electric machine; the apparatuscomprising a magnetizing device, and a frame for fitting the magnetizingdevice to a stator of the electric machine; and the frame beingconfigured for insertion inside a seat of the stator, in place of atleast one stator segment.

The present disclosure provides the activating apparatus capable ofactivating the electric machine after the rotor is fitted to the stator,and also allows the electric machine to be reactivated directly on thesystem in which it is installed, without having to dismantle andtransport it to a factory specially equipped for the job.

Another object of the present disclosure is to provide an electricmachine configured to eliminate certain of the above-described drawbacksof known electric machines.

According to one embodiment of the present disclosure, there is providedan electric machine comprising a stator, and a rotor which rotates abouta first axis with respect to the stator; the stator comprising aplurality of stator segments arranged about the first axis; the rotorcomprising modules made of magnetizable material and arranged about thefirst axis; the stator being configured to temporarily house amagnetizing device, for magnetizing the modules of magnetizable materialof the rotor, inside a seat configured for at least one of the statorsegments; the rotor being connected to the stator by a single bearing;and the magnetizing device being insertable externally from the oppositeside to the bearing.

The present disclosure provides an electric machine that can beactivated after it is installed in a system.

Additional features and advantages are described in, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A number of non-limiting embodiments of the present disclosure will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows a front view, with parts removed for clarity, of anelectric machine activatable using the method according to the presentdisclosure;

FIG. 2 shows a larger-scale, partly sectioned front view, with partsremoved for clarity, of the FIG. 1 electric machine, and an electricmachine activating apparatus in accordance with the present disclosure;and

FIG. 3 shows a larger-scale section, with parts removed for clarity, ofa detail in FIG. 2.

DETAILED DESCRIPTION

Referring now to the example embodiments of the present disclosureillustrated in FIGS. 1 to 3, number 1 in FIG. 1 indicates an electricmachine.

In the example shown, electric machine 1 may be an electric generator,such as used on a wind power system for producing electric power, or anelectric motor, such as used on a cable transportation system.

Electric machine 1 comprises a stator 2; and a hollow rotor 3 whichrotates about an axis A1 with respect to stator 2.

With reference to FIG. 2, stator 2 comprises an outer cylinder 5;cooling fins 6 fixed to the outer face of outer cylinder 5; and aplurality of stator segments 7 arranged about axis A1 (FIG. 1) and fixedto the inner face of outer cylinder 5 by fastening devices (not shown inthe drawings).

Cooling fins 6 cool outer cylinder 5 and therefore stator 2. Morespecifically, cooling fins 6 and outer cylinder 5 are made ofheat-conducting material, so that the Joule-effect or other types ofheat produced inside stator 2 is transferred to outer cylinder 5, andfrom this to cooling fins 6, by which it is dissipated.

Outer cylinder 5 therefore covers, protects, and supports statorsegments 7.

Each stator segment 7 comprises windings wound about packs of statorlaminations 8, so that each stator segment 7 can be extracted fromstator 2 without interacting with the other stator segments 7.

With reference to FIG. 1, rotor 3 comprises an inner cylinder 10; a gear11; and rotor segments 12 arranged about axis A1.

With reference to FIG. 2, each rotor segment 12 comprises a gripper 13;magnetic guides 14; modules 15 of magnetizable material; and bolts.

With reference to FIG. 3, inner cylinder 10 is connected by a bearing 16to outer cylinder 5 of stator 2. In one such embodiment, electricmachine 1 comprises only one bearing 16.

With reference to FIG. 2, modules 15 of magnetizable material arearranged about axis A1.

In each rotor segment 12, modules 15 of magnetizable material arearranged in groups. More specifically, each group of modules 15comprises two modules 15 arranged radially with respect to axis A1 (FIG.1). As shown in FIG. 3, the groups of modules 15 are arranged parallelto axis A1 along the whole of rotor segment 12.

In the non-limiting example shown, though not necessarily, each rotorsegment 12 comprises eleven groups of modules 15.

With reference to FIG. 2, each module 15 has a plane of symmetry P1; thetwo modules 15 in each group have coincident planes of symmetry P1; andthe modules 15 in each rotor segment 12 also have coincident planes ofsymmetry P1.

Each group of modules 15 is located between a respective pair ofmagnetic guides 14 defined by two packs of rotor laminations (i.e., eachgroup of modules 15 is located between two packs of rotor laminations),so each rotor segment 12 comprises eleven pairs of magnetic guides 14.Each pair of magnetic guides 14 is located inside gripper 13, is boltedto inner cylinder 10, has two faces 17 and, in use, is traversed by, andorients magnetic flux coupled to modules 15 of magnetizable material.

Modules 15 are made of material that can be magnetized by a magnetizingprocess, and which normally comprises rare-earth chemical elements, suchas samarium-cobalt or neodymium-ferroboron, and metals. It isunderstood, however, that the protective scope of the present disclosurealso covers any module 15 made of material that can be magnetized by amagnetizing process.

Electric machine 1, be it a generator or motor, must be activated (Le.,must have a magnetized rotor 3 to produce a magnetic field) and thusmodules 15 of rotor 3 must be magnetized.

According to one embodiment of the present disclosure, there is providedan apparatus 19 for activating electric machine 1, and which comprises amagnetizing device 20; a frame 21; and a precision positioning system 22fitted to frame 21, magnetizing device 20, and rotor 3.

More specifically, precision positioning system 22 comprises a precisionaxial feed device 23 fitted to frame 21; a precision rotation device 24(FIG. 1) fitted to rotor 3 and stator 2; and a fine-adjustment device 25fitted to frame 21.

With reference to FIG. 2, to activate electric machine 1, activatingapparatus 19 is positioned partly inside stator 2. More specifically,magnetizing device 20, frame 21, precision axial feed device 23, andfine-adjustment device 25 are inserted inside a seat 9 of stator 2configured to house one of stator segments 7.

In other words, in the illustrated embodiment, when activating electricmachine 1, all the stator segments 7 of stator 2 except one areassembled, so that the seat of the unassembled stator segment 7 definesseat 9, in which to insert magnetizing device 20, frame 21, and part ofprecision positioning system 22.

It is understood, however, that the protective scope of the presentdisclosure also extends to leaving two or more stator segments 7unassembled.

In an alternative embodiment (not shown) of the present disclosure, seat9 is configured to house any number of stator segments 7 more than one;in which case, when activating the electric machine, all aH the statorsegments 7 except a designated number are assembled.

With reference to FIG. 2, frame 21 is inserted inside stator 2. Morespecifically, it is fixed to outer cylinder 5 of stator 2 by fasteningdevices (not shown), and is substantially the same size as seat 9.

Frame 21 supports and surrounds magnetizing device 20 which, in use,faces one of rotor segments 12.

Each rotor segment 12, as stated, comprises modules 15 arranged parallelto axis A1 (FIG. 1). Internally, magnetizing device 20 comprises atleast one coil (not shown) which generates magnetizing flux to magnetizemodules 15; and inner magnetic guides (not shown) which conduct themagnetizing flux outwards. And externally, magnetizing device 20 has twofaces 26, through which the magnetizing flux travels, and which, in use,must completely face the two faces 17 of a pair of magnetic guides 14 toconduct the magnetizing flux effectively to modules 15 located betweenthe pair of magnetic guides 14.

Faces 26 of magnetizing device 20 are symmetric with respect to a planeof symmetry P2 of magnetizing device 20.

With reference to FIG. 3, precision axial feed device 23 substantiallyextends along an axis A2 parallel to axis A1, moves magnetizing device20 parallel to axis A2 to position faces 26 of magnetizing device 20completely facing faces 17 of pairs of magnetic guides 14 of successivemodules 15, and comprises a screw-nut screw system configured to permitprecise movement of magnetizing device 20, and to withstand theextremely strong interacting forces produced when magnetizing device 20generates magnetic flux to magnetize modules 15.

After magnetizing all the modules 15 of one rotor segment 12,magnetizing device 20 must be positioned facing another rotor segment 12with modules 15 to be magnetized. To do this, as shown in FIG. 1, rotor3 is rotated by precision rotation device 24, which meshes with gear 11fixed to rotor 3. With reference to FIG. 1, precision rotation device 24comprises a pinion 28 which is connected to stator 2, meshes with gear11 fitted to rotor 3, and is controlled by a motor and a control unit(not shown in the drawings). Rotation of rotor 3 can thus be controlled,when activating electric machine 1, to position magnetizing device 20completely facing one of stator segments 12 (FIG. 2).

With reference to FIG. 2, fine-adjustment device 25 comprises anadjusting system with articulated arms, which provides for movingmagnetizing device 20 crosswise to axis A2 with respect to frame 21.More specifically, magnetizing device 20 is supported on one side by twosupporting faces 30 of frame 21, and on the opposite side by a guide(not shown) fixed to precision axial feed device 23. Supporting faces 30and the guide curve slightly about axis A1. By the articulated arms,fine-adjustment device 25 thus provides for moving magnetizing device 20angularly about axis A1 with respect to stator 2, to fine-adjust theposition of magnetizing device 20 so that faces 26 of magnetizing device20 completely face faces 17 of a pair of magnetic guides 14, or to alignplane P2 of magnetizing device 20 with plane P1 of the group of modules15 to be magnetized. Alternatively, fine-adjustment device 25 comprisesan arm, and supporting faces 30 and the guide fixed to precision axialfeed device 23 are straight, so that the fine-adjustment device movesmagnetizing device 20 crosswise to axis A2 with respect to frame 21, andin particular tangentially with respect to stator 2, to fine-adjust theposition of magnetizing device 20.

Activating apparatus 19 comprises a temperature sensor 29, which may beof any type, such as a contact temperature sensor or a non-contact(e.g., an infrared) temperature sensor, which determines the temperatureof the group of modules 15 to be magnetized.

According to one embodiment of the present disclosure, electric machine1 described above is activated as follows.

The activating method according to one embodiment of the presentdisclosure comprises:

(a) connecting inner cylinder 10 of rotor 3 to outer cylinder 5 ofstator 2 with bearing 16;

(b) assembling two modules 15 to form the group of modules 15; fittingthe group of modules 15 to the respective pair of magnetic guides 14;fitting the pair of magnetic guides to gripper 13; repeating the aboveoperations until gripper 13 comprises eleven groups of modules 15 andeleven respective pairs of magnetic guides; and bolting gripper 13 toinner cylinder 10;

(c) repeating step (b) for each segment 12 of rotor 3, until the wholeof inner cylinder 10 of rotor 3 is fitted with rotor segments 12 withmodules 15 of magnetizable material;

(d) fitting a number of the plurality of stator segments 7 to outercylinder 5 with fastening devices, to define seat 9 for housing at leastone further stator segment 7, wherein outer cylinder 5 is fitted withall of stator segments 7 except one (the number of the plurality ofstator segments 7 equals all the stator segments 7 except one);

(e) inserting part of activating apparatus 19, in particular magnetizingdevice 20, inside seat 9 from the opposite side to bearing 16; andaligning magnetizing device 20 with a first group of modules 15 (e.g.,the group of modules 15 furthest from bearing 16);

(f) rotating rotor 3 in a controlled manner with precision rotationdevice 24 and/or fine-adjusting the position of magnetizing device 20with fine-adjustment device 25, to position faces 26 of magnetizingdevice 20 completely facing faces 17 of a pair of magnetic guides 14 ofa rotor segment 12;

(g) determining the temperature of the group of modules 15 withtemperature sensor 29;

(h) magnetizing the group of modules 15 of the pair of magnetic guides14 facing magnetizing device 20;

(i) moving magnetizing device 20 in a direction parallel to axis A2 withprecision axial feed device 23, to position the two faces 26 ofmagnetizing device 20 completely facing two faces 17 of the pair ofmagnetic guides 14 adjacent to said pair of magnetic guides 14;performing steps (g) and (h); and repeating the operation until all thegroups of modules 15 of the rotor segment 12 facing magnetizing device20 are magnetized;

(l) rotating rotor 3 in controlled manner with precision rotation device24 and/or fine-adjusting the position of magnetizing device 20 withfine-adjustment device 25, to position faces 26 of magnetizing device 20completely facing faces 17 of a pair of magnetic guides 14 of a furtherrotor segment 12 to be magnetized;

(m) repeating steps (g) to (I) to magnetize all the groups of modules 15of rotor 3;

(n) extracting magnetizing device 20 from seat 9 from the opposite sideto bearing 16, and inserting the further stator segment 7 inside seat 9.

Electric machine 1 is thus activated by the above method.

The method also provides for reactivating the activated electric machine1 by:

(o) extracting one of stator segments 7 from stator 2, on the oppositeside to bearing 16, to define the vacant seat 9 of stator 2; and

(p) performing steps (e) to (n).

The above method thus provides for reactivating electric machine 1 andremagnetizing rotor 3 directly on the system in which the machine isinstalled (i.e., with no need to dismantle the machine and transfer itto the factory for remagnetization).

In one variation, the method according to the present disclosurecomprises, between steps (g) and (h), the additional step of:temperature-conditioning the group of modules 15 with a temperatureconditioning system connected to modules 15, to achieve a suitablemagnetization temperature of modules 15.

In one variation of the method according to the present disclosure, step(f) of rotating rotor 3 in controlled manner with precision rotationdevice 24 and/or fine-adjusting the position of magnetizing device 20with fine-adjustment device 25 is performed in such a manner as to alignplane P2 with plane P1 of at least one of modules 15.

Electric machine 1 described is a radial-flux, buried-permanent-magnettype. It is understood, however, that the scope of the presentdisclosure also extends to any other type of permanent-magnet electricmachine, such as a radial-flux, surface-magnet or axial-flux orcross-flux electric machine.

In an alternative embodiment (not shown in the drawings), themagnetizing device is larger than the one shown in FIG. 2, andsimultaneously magnetizes more than one group of modules, such as twogroups of modules, or all the groups of modules forming part of therotor segment or two or more rotor segments. In which case, the faces ofthe magnetizing device face more than two faces of the pairs of magneticguides.

In an alternative embodiment (not shown in the drawings), themagnetizing device is housed in a stator seat corresponding to anynumber of stator segments other than one, e.g. to two, three or morestator segments.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A method of activating an electric machine, said method comprising:coupling a rotor to a stator, the rotor configured to rotate about axiswith respect to the stator, wherein: (a) the rotor includes a pluralityof rotor segments, each rotor segment including; i) a plurality ofmodules of magnetizable material, and (ii) a pair of magnetic guideshaving respective first faces and configured to conduct a magnetic fluxcoupled to said respective modules, and (b) the stator includes: (i) anouter cylinder, and (ii) a plurality of slidably removable statorsegments arranged about the first axis, wherein at least two of theplurality of stator segments are fitted to the outer cylinder of thestator to define a seat configured to house at least another one of saidstator segments; inserting a magnetizing device in the seat, themagnetizing device having two second faces and configured to provide themagnetizing flux; positioning the magnetizing device such that thesecond faces of the magnetizing device face the first faces of at leastone of the pairs of magnetic guides; and after coupling the rotor to thestator, magnetizing at least one of said plurality of modules ofmagnetizable material.
 2. The method of claim 1, which includes slidablymoving the magnetizing device along the rotor segment such that thesecond faces of the magnetizing device face the first faces of at leastanother one of the pairs of magnetic guides.
 3. The method of claim 1,wherein the modules of the rotor are arranged in a plurality of groups,each module is symmetric with respect to a first plane of symmetry, ineach of the groups, the modules in said group have coincident firstplanes of symmetry, the modules in each rotor segment have coincidentfirst planes of symmetry, and the second faces of the magnetizing deviceare symmetrical with respect to a second plane of symmetry, and whichincludes positioning the magnetizing device such that the second facesof the magnetizing device face the first faces of at least one of thepairs of magnetic guides.
 4. The method of claim 3, which includespositioning the magnetizing device such that the first plane coincideswith the second plane.
 5. The method of claim 1, which includes fittingat least two of the plurality of stator segments to the outer cylinderof the stator to define the seat.
 6. The method of claim 1, whichincludes moving the magnetizing device along one of the rotor segmentsof the rotor in a direction parallel to the first axis such that thesecond faces of the magnetizing device face the first faces of at leastanother one of the pairs of magnetic guides.
 7. The method of claim 1,which includes rotating the rotor to position the magnetizing device toface another one of the plurality of rotor segments of the rotor to bemagnetized.
 8. The method of claim 1, which includes fine-adjusting theposition of the magnetizing device by moving the magnetizing deviceangularly or tangentially with respect to the stator.
 9. The method ofclaim 1, which includes: extracting the magnetizing device from theseat, and inserting one of the stator segments in the seat.
 10. Themethod of claim 1, which includes, prior to magnetizing said pluralityof modules: extracting at least one of the stator segments to define theseat, and inserting the magnetizing device in the seat.
 11. The methodof claim 1, which includes controlling the temperature of the modules.12. An electric machine activating apparatus comprising: a magnetizingdevice; and a frame configured to fit the magnetizing device to a statorof an electric machine, the frame being configured to be inserted in aseat of the stator in place of at least one stator segment, wherein theframe is configured to fit to an outer cylinder of the stator such thatthe magnetizing device faces a rotor of the electric machine.
 13. Theelectric machine activating apparatus of claim 12, wherein themagnetizing device is supported by the frame and is configured tomagnetize the rotor of the electric machine with magnetizing flux. 14.The electric machine activating apparatus of claim 12, which includes aprecision positioning system having a precision rotation device fittedto the rotor and the stator of the electric machine, said precisionpositioning system configured to rotate the rotor to position themagnetizing device to face at least one rotor segment of the rotor, saidprecision rotation device including a precision axial feed deviceconfigured to move the magnetizing device in a direction correspondingto an axis and to position the magnetizing device to face at least onemodule of magnetizable material of the rotor.
 15. The electric machineactivating apparatus of claim 14, wherein the precision axial feeddevice includes a screw-nut screw system.
 16. The electric machineactivating apparatus of claim 14, wherein the precision positioningsystem includes a fine-adjustment device configured to move themagnetizing device crosswise to the axis with respect to the frame. 17.The electric machine activating apparatus of claim 14, wherein eachmodule has a first plane of symmetry, the magnetizing device has twosecond faces symmetrical with respect to a second plane of symmetry, andthe precision positioning system includes a fine-adjustment deviceconfigured to fine-adjust a position of the magnetizing device.
 18. Theelectric machine activating apparatus of claim 17, wherein thefine-adjustment device is configured to fine-adjust the position of themagnetizing device such that the second plane of symmetry coincides withthe first plane of symmetry of at least one of the modules.
 19. Theelectric machine activating apparatus of claim 12, wherein the frame isconfigured to fit to the outer cylinder of the stator such that themagnetizing device faces the rotor of the electric machine.
 20. Theelectric machine activating apparatus of claim 12, which includes atemperature sensor.
 21. An electric machine comprising: a statorincluding a plurality of stator segments arranged about a first axis,the stator configured to house a magnetizing device in a seat configuredfor at least one of the stator segments, wherein the magnetizing deviceis configured to be inserted externally; a rotor configured to rotateabout the first axis with respect to the stator, the rotor including aplurality of modules of magnetizable material and arranged about thefirst axis, wherein the magnetizing device is configured to magnetizethe modules of magnetizable material; and a single bearing configured tocouple the stator and the rotor.
 22. The electric machine of claim 21wherein each of the stator segments is configured to be extracted fromthe stator without interacting with the other stator segments.
 23. Theelectric machine of claim 21, wherein the modules of the rotor arearranged in a plurality of groups, each module has a plane of symmetry,and in each of the groups, the modules of said group have coincidentplanes of symmetry.
 24. The electric machine of claim 21, wherein therotor includes a plurality of pairs of magnetic guides having respectivefirst faces and configured to conduct a magnetic flux coupled to saidrespective modules such that each pair of magnetic guides is traversedby and configured to orient magnetic flux coupled to the modules ofmagnetizable material.
 25. The electric machine of claim 21, wherein thestator is configured to temporarily house the magnetizing device in theseat.
 26. The electric machine of claim 21, wherein the magnetizingdevice is positioned at a plurality of the stator segments.
 27. Anelectric machine comprising: a stator including a plurality of statorsegments arranged about a first axis, the stator configured to house amagnetizing device in a seat configured for at least one of the statorsegments, the magnetizing device is configured to be slidably insertedexternally; a rotor configured to rotate about the first axis withrespect to the stator, the rotor including a plurality of modules ofmagnetizable material and arranged about the first axis, wherein themagnetizing device is configured to magnetize the modules ofmagnetizable material; and a bearing configured to couple the stator andthe rotor.
 28. A method of activating an electric machine including astator having a plurality of stator segments arranged about a firstaxis, a rotor including a plurality of modules of magnetizable materialand arranged about the first axis, said rotor configured to rotate aboutthe first axis with respect to the stator, said method comprising:coupling the rotor to the stator by a bearing; inserting a magnetizingdevice in a frame; slidably inserting the frame in a seat of theelectric machine; and after coupling the rotor to the stator,magnetizing said magnetizable material of the modules.
 29. The method ofclaim 28, which includes fitting each of said modules to the rotor whensaid modules are each non-magnetized.
 30. The method of claim 28, whichincludes: fitting at least two of the plurality of stator segments to anouter cylinder of the stator to define the seat configured to house atleast another one of the stator segments; and inserting the magnetizingdevice in the seat.
 31. The method of claim 28, wherein the rotorincludes a plurality of rotor segments which include said modulesaligned parallel to the first axis, and which includes magnetizing eachmodule of the rotor segment facing the magnetizing device.
 32. Themethod of claim 31, which includes rotating the rotor to position themagnetizing device to face another one of the rotor segments to bemagnetized.
 33. The method of claim 28, wherein each of said modules hasa first plane of symmetry, the magnetizing device has two second facessymmetrical with respect to a second plane of symmetry, and whichincludes positioning the magnetizing device such that the second planeof symmetry coincides with the first plane of symmetry of at least oneof the modules.
 34. The method of claims 28, wherein the rotor includesa plurality of pairs of magnetic guides having respective first facesand configured to conduct a magnetic flux coupled to the respectivemodules by the first faces, the magnetizing device has two second facesand is configured to provide the magnetizing flux via the second faces,and which includes positioning the magnetizing device such that thesecond faces of the magnetizing device face the first faces of at leastone of the pairs of magnetic guides.
 35. The method of claim 34, whichincludes moving the magnetizing device along the rotor in a directionparallel to the first axis, such that the second faces of themagnetizing device face the first faces of at least another one of thepairs of the magnetic guides.
 36. The method of claims 28, whichincludes fine-adjusting a position of the magnetizing device by movingthe magnetizing device angularly or tangentially with respect to thestator.
 37. The method of claim 28, which includes: extracting the framefrom the seat, and inserting another one of the stator segments in theseat.
 38. The method of claim 28, which includes controlling thetemperature of the modules at least when magnetizing said magnetizablematerial of the modules.